PROJECT SUMMARY Introduction: The rising incidence of autism spectrum disorders (ASD) charges researchers with a sense of urgency to develop sensitive tools for early identification. Recent advances allow experts to identify ASD in the second year through an array of social communication and motor coordination deficits. This project attempts to extend this work into infancy. Aims: The broad objectives of this research are to develop novel tools for early identification of motor, social, and cognitive deficits of Autism Spectrum Disorders (ASD) within the first six months of life. In this proposal, reaching, object exploration, and associative learning tasks are used as powerful contexts to identify impairments related to ASD and the broader autism phenotype (BAP) within the first six months of life. We will longitudinally compare two groups: 1) infant siblings of children with autism (AU Sibs), who are a cohort at high genetic risk to develop ASD and BAP impairments, and 2) typically developing, infant siblings of children with no family history of ASD (TD Sibs) at 3 and 6 months along with follow-up screening at 16 months. Methods: During reaching and object exploration, infants will be observed during single-rattle or multi-rattle conditions to probe their reaching, grasping, and visual attention/exploration patterns. In addition, during associative learning, infants will learn the relationship between their arm movements and the activation of a musical toy. We will code for learning, pattern of toy activation, and visual attention patterns. Fine-motor measures such as reaching and rhythmic arm movements will be quantified using a portable electromagnetic motion tracking system. Preliminary Findings: Our preliminary data suggest that AU Sibs tested at 3 and 6 months have reaching and grasping coordination deficits as well as excessive visual exploration during reaching and object exploration tasks. Moreover, AU Sibs show difficulty shifting visual attention during an associative learning task. Through this proposal, we build on our preliminary data and expand our database on fine-motor coordination and visual attention impairments of the AU Sibs population. Significance: This project will vastly add to our understanding of the early developmental processes that lead to the core deficits of ASD. In addition, if the aims are achieved it will identify reliable behavioral markers for early diagnosis of ASD. Specifically, the results of this study would implicate that early detection of ASD and the BAP is possible between 3 and 6 months of age through fine-motor and visual attention markers. It would also emphasize that infant siblings of children with autism are at risk for general sensori-motor delays and need sensori-motor interventions.